Bug 1125084 - Uninitialised value use in mozilla::hal_impl::SetScreenBrightness(double). r=dhylands.

hal/gonk/GonkHal.cpp

@@ -764,8 +764,11 @@ bool
 GetKeyLightEnabled()
 {
   LightConfiguration config;
-  GetLight(eHalLightID_Buttons, &config);
-  return (config.color != 0x00000000);
+  bool ok = GetLight(eHalLightID_Buttons, &config);
+  if (ok) {
+    return (config.color != 0x00000000);
+  }
+  return false;
 }
 
 void
@@ -798,10 +801,15 @@ GetScreenBrightness()
   LightConfiguration config;
   LightType light = eHalLightID_Backlight;
 
-  GetLight(light, &config);
-  // backlight is brightness only, so using one of the RGB elements as value.
-  int brightness = config.color & 0xFF;
-  return brightness / 255.0;
+  bool ok = GetLight(light, &config);
+  if (ok) {
+    // backlight is brightness only, so using one of the RGB elements as value.
+    int brightness = config.color & 0xFF;
+    return brightness / 255.0;
+  }
+  // If GetLight fails, it's because the light doesn't exist.  So return
+  // a value corresponding to "off".
+  return 0;
 }
 
 void